Carotid diameter improves the carotid IMT capacity to predict coronary events: data from the IMPROVE study

Introduction: The “IMPROVE study” is a prospective, longitudinal study designed to investigate whether cross-sectional carotid artery intima media thickness (C-IMT) and C-IMT progression are predictors of vascular events in European individuals at high risk of cardiovascular diseases. Objective of the present study was to investigate whether C-IMT could be combined with inter-adventitial common carotid artery diameter (ICCAD) to improve the current capacity to predict vascular events over and above that provided by Framingham risk factors (FRFs). Methods: 3711 subjects (median age 64.4 years; 48% men) with at least three vascular risk factors (VRFs) were recruited in 7 centers of 5 European countries (Finland, France, Italy, the Netherlands and Sweden). 3703 patients (median age 64.4 years, 48% men) were monitored for a median follow up of 36.2 months. During this period, 215 patients suffered a first cardiovascular event with an incidence of 19.9 per 1000 person-years. Results: By Cox proportional hazard regression analysis, all measures of C-IMT and ICCAD were independently associated with risk of any vascular event; associations persisted after adjustment for age, gender, traditional risk factors and pharmacological treatments (Ptrend<0.005 for all). Results were mostly significant also when cardio, cerebro and peripheral vascular events were considered separately. Composite C-IMTs (IMTmean and IMTmean-max) as well as combinations of C-IMT variables and ICCAD yielded stronger relations than common carotid IMT alone. Compared to classification based on FRFs alone, the net reclassification improvement resulting from the combination of FRFs + ICCAD + IMTmean and that of FRFs + ICCAD + IMTmean-max were +11.4% and +12.1%, respectively. Conclusions: C-IMTs and ICCAD are independent predictors of vascular events in European high-risk subjects and together they significantly enhance the predictive capacity of VRFs.